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At the top of Twitter's 'The 10 Most Powerful Tweets of 2010' list, when a Doctors Without Borders plane could not get clearance to land in earthquake-ravaged Haiti, reporter Ann Curry tweeted: @usairforce find a way to let Doctors without Borders planes land in Haiti: http://bit.ly/8hYZOK THE most effective at this. She convinced the US Air Force to let the plane land. A woman walks by a pile of rubble on the streets of Port-au-Prince, Haiti, on Jan. 16. Mary Knox Merrill/The Christian Science Monitor

The White house extended a warm Twitter welcome to Russian President Dmitry Medvedev with the following tweet – and retweet: Welcome to @twitter President Medvedev! RT @KremlinRussia_E: Hello everyone! I'm on Twitter, and this is my first tweet. President Medvedev (l.) meets with President Barack Obama on the sidelines of the APEC summit in Yokohama, Japan, on Nov. 14. Dmitry Astakhov/RIA Novosti/Presidential Press Service/AP

'Catastrophe is a strong word, let's all agree to call it a whoopsie daisy.' It came as no surprise that this tweet was an impostor, written not by BP about its Deepwater Horizon oil spill in the Gulf of Mexico, but by a Twitter account called BPGlobalPR. The Deepwater Horizon oil rig burns in this aerial photo taken more than 50 miles southeast of Venice, Louisiana, on April 21. Gerald Herbert/AP

Another spoof Twitter account called alqaeda tweeted: Just noticed Twitter keeps prompting me to 'Add a location to your tweets'. Not falling for that one. This image made from video broadcast in 2001 shows Osama bin Laden at an undisclosed location. Al-Jazeera/AP/FILE

Ashton and CNN battle to 1 million: In early 2009, actor Ashton Kutcher challenged cable network CNN to a race to see who could be the first Twitter user to attract 1 million followers. Mr. Kutcher emerged victorious that April. Since then, many celebrities have passed the million benchmark, and Kutcher’s feed, @APlusK, has surpassed 4.6 million. Alexander Zemlianichenko/AP

'Miracle on the Hudson': Janis Krums provided one of the early demonstrations that Twitter could be more than a way to keep up with what your friends ate that day. On January 15, 2009, Captain Chesley "Sully" Sullenberger safely landed a U.S. Airways plane on the Hudson River after a flock of geese disabled its engines. Before traditional media had the story, Mr. Krums took a picture of the downed plane and posted it to Twitter. The now-famous TwitPic attracted more than half a million views and proved that Twitter could be a source for breaking news. Brendan McDermid/Reuters/FILE

Oprah embraces Twitter: In April 2009, Twitter got perhaps its biggest celebrity nod. Not a tech-industry type, or someone popular with the kids. Twitter snagged Oprah Winfrey, the TV luminary and gatekeeper to a brand new audience for the social website. Twitter cofounder Evan Williams joined Winfrey on her Friday talk show and walked millions of viewers through the process. Oprah’s first message? 'HI TWITTERS. THANK YOU FOR A WARM WELCOME. FEELING REALLY 21st CENTURY.' George Burns/Harpo Productions/AP

Twitter goes green for Iran: During the 2009 Iranian election, thousands of protesters took to the streets to speak out against alleged electoral fraud and to support opposition candidate Mir-Hossein Mousavi. Twitter played a role in the protests both in Iran and around the world. Organizers in Iran used the online service to spread news, safety warnings, and locations of political rallies. Outside of the country, many Twitter users tinted their profile icon green to show solidarity with this so-called Green Revolution. Here, an Iranian student gestures during a protest on Feb. 11 in Singapore. About 30 Iranian students wore green clothes and held signs reading "Iran wants freedom" and "Stop human rights violations against students in Iran" along with photos of protesters who the students said had been killed by government security forces in Iran. Wong Maye-E/AP

Twestival raises $250,000: 'Twestival' – an event whose name blends 'Twitter' and 'festival' – turned the social site into a force for good. The organizers used Twitter to schedule a series of 200 off-line charity events around the globe, from concerts in New York to knitting groups in Brussels, that raised a combined $250,000 from 10,000 new donors. A Village in Ethiopia use clean water for the first time from a well provided by Charity: Water. Courtesy of Scott Harrison/Charity: Water

Mars rover announces discovery of water: When the Mars Phoenix Lander found water on Mars, NASA spread the word via Twitter. 'Are you ready to celebrate? Well, get ready: We have ICE!!!!! Yes, ICE, *WATER ICE* on Mars! w00t!!! Best day ever!!' tweeted the Phoenix Lander’s Twitter feed. Here, the Mars rover, Opportunity, casts a shadow in Nov. 2004. Cornell/JPL/NASA/AP

Indie flick Paranormal Activity becomes blockbuster: Thanks to very clever marketing on Twitter and Facebook, 'Paranormal Activity' went from anonymous horror flick to the No. 1 movie in America. First-time director Oren Peli spent just $15,000 making the film. But after a social-media blitz, the movie raked in more than $107 million. Paramount/AP

First Tweet from space: On Jan. 10, 2010, NASA astronaut TJ Creamer sent the first live tweet from outer space. 'Hello Twitterverse!' Mr. Creamer typed from the International Space Station. 'We r now LIVE tweeting from the International Space Station -- the 1st live tweet from Space! :) More soon, send your ?s.' The newly installed cupola windows in the International Space Station were 'tweeted' from space by JAXA astronaut and Expedition 22 flight engineer Soichi Noguchi on Feb. 17. The $27-million, Italian-built port gives the station crew a commanding view of Earth and approaching cargo vessels. NASA/Reuters

Businesses flock to Twitter :Whenever something becomes popular, marketers are always close behind. But some companies got creative when they joined Twitter. JetBlue and United Airlines tip off Twitter users to last-minute empty seats – some for as low as $9 for a one-way flight. Last summer, Dell bragged that it brought in an extra $3 million in revenue by advertising sales and special deals through @delloutlet. And Whole Foods (pictured here) uses its feed to improve customer service. John Nordell/The Christian Science Monitor/FILE

San Diego fire emergency updates via tweet: When wildfires swept through San Diego in 2007, Twitter became a key source of updates and safety information. Several news organization, including local TV station KPBS, posted regular tweets as the event unfolded. Here, San Marcos Fire Department firefighters watch over a burning ravine near Julian, Calif., in September 2007. Earnie Grafton/San Diego Union-Tribune/AP

When people think of Twitter, they usually think of clipped comments about pop culture or the minutia of daily life, not formal legal documents and procedures. But that may be about to change in the United Kingdom, where the highest court in the country announced on Monday that it would begin accepting freedom of information (FOI) requests through Twitter.